[Coco] DW and 6551

[Aaron Wolfe]

In theory a UART would be a lot more efficient than the bitbanger.
However, in reality, Darren's awesome bitbanger routines are so much faster
than the 6551 can go that it doesn't work out that way in this particular
situation.  If we had a 16550 or more modern uart then I suspect things
would swing the other way, but since drivewire is kind of for people that
don't have a lot of hardware to start with I doubt we could get many folks
onboard with a whole new serial card.  Better to skip past that right into
ethernet or wifi.
On Feb 10, 2015 8:30 PM, "Allen Huffman" <alsplace at pobox.com> wrote:

> > On Feb 10, 2015, at 5:35 PM, Aaron Wolfe <aawolfe at gmail.com> wrote:
> >
> > There was a driver at one point, but I don't think anyone maintains it
> and
> > so I don't think it was converted to the modular system we started using
> a
> > while back.  In the time since that document was written I think it's
> > realistically changed to "not supported".  Writing a driver for the 6551
> > would not be very difficult but since it's so limited in speed compared
> to
> > the bitbanger I think there is little interest.
>
> At a reduction of speed, would we get better responsiveness by using the
> hardware, though? I was stunned to find that I could use 9600 baud on /t1 a
> few nights ago. If I typed real fast it would glitch a character, but it
> was working. I knew this was easy in RS-DOS, but thought the bitbanger code
> was limited to like 1200 or so.
>
> BUT, it really chewed up the system and made everything hang and pause. I
> note that bitbanger DW does the same thing, which is fine if you aren’t
> multitasking but I tend to always be doing something. I wonder if the RS232
> pak would be a good tradeoff — less IRQ masking but slower disk transfers.
>
> One of the big myths back in the day was the limit of the bitbanger. It
> was rare to see terminal programs that went very fast, but Ultimaterm (and
> probably Sockmaster’s) proved it could be done. We used a remote drive
> written by Ken Johnson (Johnston?) who wrote Ultimaterm and it went to a
> higher baud rate than anything we knew about - - complete with a typeahead
> buffer in BASIC.
>
> I was very impressed /t1 could do that kind of stuff now — I am guessing
> it got upgraded because of new knowledge gained from DW? Or has it always
> worked and we were just told it was impossible so we never tried?
>
>                 — A
>
> --
> Coco mailing list
> Coco at maltedmedia.com
> https://pairlist5.pair.net/mailman/listinfo/coco
>